The main thrust of our work is concerned with the mechanism of action and the biological function of ribonuclease H (hybridase). Other problems to be investigated are concerned with the enzymes handling nucleic acids in developing chicken embryos. BIBLIOGRAPHIC REFERENCES: E. Chargaff, Initiation of Enzymic Synthesis of Deoxyribonucleic Acid by Ribonucleic Acid Primers, Progr. Nucleic Acid Res., 16, 1-24 (1976). J.G. Stavrianopoulos, A. Gambino-Giuffrida, and E. Chargaff, Ribonuclease H of Calf Thymus: Substrate Specificity, Activation, Inhibition, Proc. Nat. Acad. Sci. 73, 1087-1091 (1976).